A Small Antigenic Determinant of the Chikungunya Virus E2 Protein Is Sufficient to Induce Neutralizing Antibodies which Are Partially Protective in Mice

Abstract

BackgroundThe mosquito-borne Chikungunya virus (CHIKV) causes high fever and severe joint pain in humans. It is expected to spread in the future to Europe and has recently reached the USA due to globalization, climate change and vector switch. Despite this, little is known about the virus life cycle and, so far, there is no specific treatment or vaccination against Chikungunya infections. We aimed here to identify small antigenic determinants of the CHIKV E2 protein able to induce neutralizing immune responses.Methodology/Principal FindingsE2 enables attachment of the virus to target cells and a humoral immune response against E2 should protect from CHIKV infections. Seven recombinant proteins derived from E2 and consisting of linear and/or structural antigens were created, and were expressed in and purified from E. coli. BALB/c mice were vaccinated with these recombinant proteins and the mouse sera were screened for neutralizing antibodies. Whereas a linear N-terminally exposed peptide (L) and surface-exposed parts of the E2 domain A (sA) alone did not induce neutralizing antibodies, a construct containing domain B and a part of the β-ribbon (called B+) was sufficient to induce neutralizing antibodies. Furthermore, domain sA fused to B+ (sAB+) induced the highest amount of neutralizing antibodies. Therefore, the construct sAB+ was used to generate a recombinant modified vaccinia virus Ankara (MVA), MVA-CHIKV-sAB+. Mice were vaccinated with MVA-CHIKV-sAB+ and/or the recombinant protein sAB+ and were subsequently challenged with wild-type CHIKV. Whereas four vaccinations with MVA-CHIKV-sAB+ were not sufficient to protect mice from a CHIKV infection, protein vaccination with sAB+ markedly reduced the viral titers of vaccinated mice.Conclusions/SignificanceThe recombinant protein sAB+ contains important structural antigens for a neutralizing antibody response in mice and its formulation with appropriate adjuvants might lead to a future CHIKV vaccine.

Identification of Functional Determinants in the Chikungunya Virus E2 Protein

“…Binding was detected as the mean change in fluorescence. In addition, the CHIKV E2-derived protein sA (containing the surface exposed regions of domain A connected by linkers) [ 23 ] was used as a negative control for the binding of E . coli derived proteins and the Fc-protein served as negative control for Fc-fusion proteins and the values are given as fold increase in binding compared to Fc.…”

Structural Studies of Chikungunya Virus-Like Particles Complexed with Human Antibodies: Neutralization and Cell-to-Cell Transmission

“…A construct containing the B domain and the ␤ ribbon produced neutralizing antibodies in mice (31). Furthermore, a peptide of domain A fused with domain B, and the ␤ ribbon induced potent antibodies.…”

Cellular and Molecular Immune Response to Chikungunya Virus Infection

“…Both in humans and mice the antibody-mediated immune response seems to primarily target the envelope glycoprotein E2 of CHIKV (Kam et al, 2012a ; Smith et al, 2015 ; Weber et al, 2015 ; Weger-Lucarelli et al, 2015 ). Moreover, the majority (70–80%) of the antibodies are estimated to be directed against the single linear epitope (E2EP3) in the N-terminus of the viral E2 protein.…”